Illuminating structure.



PATENTED JAN. 27, 1903.

I. L. 0. WADSWORTH. ILLUMINATIN G STRUCTURE APPLICATION FILED OCT. 28.1898.

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10 MODEL.

WITNESSES m: "ohms vzrzns co, vHcm-uma, WASHINGTON, o c.

PATENTED JAN. 27, 1903. I

F. 'L. 0. WADSWORTH. ILLUMINATING STRUCTURE.

APPLICATION FILED OCT. 28, 1898.

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WITNESSES No. 719 066. PATBNTED JAN. 27, 19.03.

v P. L. 0. WADSWQRTH. ILLUMIN ATIN G STRUCTURE.

APPLICATION FILED 001. 28, 1898.

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FRANK L. O. WVADSWORTI-I, OF YVILLIAMS BAY, WISCONSIN, ASSIGNOR TOPRESSED PRISM PLATE GLASS COMPANY, A CORPORATION OF WEST VIRGINIA.

ILLUMINATING STRUCTURE.

SPECIFICATION forming part of Letters Patent No. 719,066, dated January27, 1903.

Application filed October 28, 1898. Serial No. 694,828. (No model.)

To rtZZ whom it may concern.-

Be it known that I, FRANK L. O. WADs- WORTH, a citizen of the UnitedStates, residing at Williams Bay, in the county of \Valworth and Stateof Wisconsin, have invented certain new and useful Improvements inIlluminating Structures, of which the following is a specification.

The object of my invention is to obviate certain difficulties incidentto the use of ordinary illuminating structures; and my inventionconsists in constructing such structures of contiguousilluminating-plates which may in some cases be relatively adjustable, asfully set forth hereinafter and as illustrated in the accompanyingdrawings, in which-- Figures 1 to 3 are sectional views ofrefracting-illuminators of different forms and adjustments embodying myinvention; Fig. 4, a diagram illustrating a method of laying off theangles of the coacting prisms, Figs. 1, 2, 3; Figs. 5 to 6, sectionalviews of structures having reflecting-prisms embodying my invention;Fig. 7, a diagram illustrating a method of laying off the angles ofstructures such as those shown in Figs. 5 and 6; Figs. 8 to 12,sectional views illustrating different constructions and arrangements ofparts in myimproved structure. Fig. 13 is a sectional View of a panelcomplete embodying my improvement.

An ordinary prismatic structure acting by refraction and receiving raysfrom any given direction in a continuous sheet discharges them from theinner side in a series of bundles, so that when the light all comes frompractically one direction the space behind the structure is irregularlyilluminated. Moreover, only a certain deviation, not much exceedingsixty degrees with ordinary kinds of glass, can be secured with one setof refracting-prisms, and this only by making the angles of incidence onthe prism-faces so large that there is great loss by reflection at thesefaces. These difficulties are both avoided by using two sets of coactingilluminating-plates with prismatic faces, as in Figs. 1 to 3. Here therays from the principal direction 1 1 1 are deflected by the first setof prisms P P in the direction 1 1 and fall upon the second set ofprisms P P, by which they are further deviated and emerge from thestructure in the required direction 1 1. By properly proportioniug thetwo sets of prisms and placing them in proper position with reference toeach other the whole bundle of rays deflected by the first set ofrefractingsurfaces 1" r r will fall upon the second set r r r, and bedeflected thereby, so as to emerge from the inner side of the structurein an unbroken sheet, as at 1 1 1. Fig. 4 is a diagram showing how thefaces 'rr' and r r are proportioned to each other to secure this result.The proper relation may be determined mathematically or graphically bytrial, as follows: Let 1 1 be the direction of the principal raysfalling on the first side M M of the structure. Trace out the direction1 which these rays take in entering the structure, using to do this therelation sin. I 'n sin. R, where I is the angle of incidence of theprincipal rays on the surface M M, n the index of refraction of theglass, and R the desired angle of refraction of the rays entering thesurface M M. Lay off also the direction 1 1 in which it is desired thatthese rays shall emerge from the inner surface N N and trace these raysback through this surface in similar manner. When the rays 1 1 emergepractically perpendicular to the surface N N, as in the figure, they ofcourse enter the same without change of direction by refraction. Takeany two points ct l) on this surface, lay off by trial a line '1' rrepresenting a refracting-surface, and trace the rays ct1, b1

back through this surface. Lay off a second surface 1' r inclined atsuch an angle that the rays just traced back through 0" r and taking thedirection 1 will enter this surface in the direction parallel to 1 andfind where these rays intersect the front surface M M. If the points ofintersection a b are farther apart than the points ab, make a trial oftwo other surfaces r r r 1", which fulfil the same condition-t. e., thatthe rays transmitted 9 from the first enter the second parallel to 1. Ifthe points of intersection a b are now closer together than the points ab, Iknow that the two proper coacting surfaces lie between 1" r and r rand r r and r r, and a third trial usually suffices to determine the twoproper surfaces 1" r and r W, which will coact in such a way that thetwo rays 1 1 emerge from the rear face at the same distance apart a Z)as the distance apart at which they entered.

Having thus determined the proper angles which the deflecting-faces r7'' make with the two surfaces M M and N N, respectively, we

lay off the other neutral surfaces 3 and s of the prisms respectivelyparallel to the directions 1 and 1, which the principal rays take in thetwo plates. If then we make the prisms on the two plates of the samewidth (measured along the planes of their respective plates) and placethe second plate so that the meeting edges of the prismatic faces are onlines parallel to the direction l of the rays between the plates, as inFig. 1, the continuous sheet of light falling on the front surface fromthe direction 1 1 1 will be transmitted through the structure and emergefrom the inner side as an unbroken sheet-2'. 6., the entire space behindN N will be uniformly illuminated in the direction 1 1 Prismaticreflecting structures as usually constructed are open to the sameobjection that has just been pointed out in connection with prismaticstructures acting by refraction.

In the operation of prismatic reflecting structures of ordinary form thesheet of light falling on the front surface is broken up by the prisms,so as to emerge as series of separate bundles. In structures heretoforepro- 5 posed this defect is overcome to a certain degree by the use ofdispersing ribs or grooves on the inner emergent surface, which break upthese separated bundles into spreading cones of light; but thisconstruction has other 0 disadvantages which need not here beenumerated.

Figs. 5, 6, 7 illustrate the application of my invention to overcomethis difficulty incident to reflecting-prisms. As before, I make use 5of two illuminating-plates M N, the prisms P on the front plate beingreflecting-prisms and the prisms of both plates projecting into theintermediate chamber. The proper inclination of the coacting frontreflecting-faces 5o '1 and the rear refracting-faces r is determinedmathematically or graphically, as before, as shown in Fig. 7, in whichlike letters of reference relate to the same trial surfaces andoperations as have already been described in connection with Fig. 4.

Figs. 8 and 10 illustrate a modification in which a continuous sheet oflight from the inner side of the structure is secured by the use on thefirst plate of prisms having concave deflecting-faces r, coacting withconvexly-curved lenses or ribs 7" on the second plate. The first concavedeflecting-faces act to diverge or spread as well as deflect the streamsof light falling upon them, so that the latter will completely cover thereceivingsurface of the second plate. In order to obtain a continuousparallel sheet of rays from the latter, it is then only necessary toprovide this surface with a series of convexly-curved lenses or ribs, sosituated that the edges of the ribs are on the lines of intersection ofthe extreme rays from contiguous prism elements, as shown in Figs. 8 and10, and of such curvature that the divergent streams of light will berendered parallel. The first deflecting-faces may be eitherreflecting-faces, as in Fig. 8, or refracting-faces, as in Fig. 10. Inthe latter case, as already stated, only rays having a certain maximuminclination to the horizontal (not generally exceeding about sixtydegrees) can be efficiently directed into the space to be illuminated ina hori- Zontal direction. An additional deflection at the curved ribsmay be secured by making these prismatic in form, as in Fig. 9, in whichcase there is obtained a combination of the effects shown in Figs. 1 and2 and in Fig. 10.

In some cases I may fill the chambers between the plates with liquid, asin Fig. 2. The angles of the prisms are then different, because of thedifference in refraction between air and the liquid used, but theprinciples governing the design are the same as already set forth.

In the building up of the illuminating structure two illuminating-platesof the character described are mounted in the frame with a chamberbetween, and preferably the de fleeting elements project inwardly intothe chamber. This protects these elements from accidental breaking, alsofrom becoming dirty, and permits the external light receiving anddischargingfaces to be substantially flat and smooth, so they may bereadily cleaned. In some cases there may be series of fiatreceiving-ribs on the outer side, as in Fig. 6, the upper sides 13nearly perpendicular to the incident rays of light and the lower faces qnearly parallel thereto. These ribs act simply to diminish the loss oflight by reflection at the front surface, as at 1 Fig. 5, and are notproperly deflecting elements. In other cases the curved ribs 1' r may beturned outward toward the rear surface, as in Fig. 10. In either casethe projecting portions are so low that they do not interfere with readycleaning of the sheet. The sheets may be placed so that theinwardly-projecting portions are practically in contact or separated toa moderate extent or widely separated, as at Fig. 10. In any case theinclosed chamber or space between the plates (which is closed on twosides by the glass sheets, on the others by the supporting-frame A) actsas an air-curtain, (which, as already stated, may be of any desiredthickness,) protecting the room from sudden change of temperature. Thestructure acts in this respect like a storm-sash. Both sheets of glassmay in certain cases be secured in a common frame, as in Fig. 6; but asthe interior space may occasionally become dusty and dirty, no matterhow great care is taken in sealing the plates into the frame, I preferto mount each plate of illuminating-glass, however constructed, in itsown frame and to secure these frames together face to face, as shown inFigs. 8, S, 10, ll, and 13. These frames can then be readilydisconnected when desired and the internal inclosed faces cleanedwithout even removing the main frame of the structure from position. Theintroduction of dirt and dust may be prevented by filling the cavitywith liquid, as in Fig. 2; but in this case also it is desirable to havethe plates separable, so that liquid may be replaced or removed whendesired. The frames may be secured together by screws or other suitablemeans in permanent relation, as illustrated in Figs. 8 and 1.0, or theymay be made adjustable longitudinally, as in Figs. 2 and 13, orlaterally or transversely, as in Fig. 5. In either case it ispracticable by such adjustment to alter the form or outline oftheinternal chamber. By this means we are enabled to alter the directionof the emergent rays or to vary the amount of light sent in the desireddirection. Thus by moving the rear prismatic plate (shown in Fig. 1)

from the position shown in that figure to that shown in Fig. 3 some ofthe rays will fall upon the neutral surfaces 8 s of the prisms P and bein consequence sent downward in the direction l 1 instead of backward inthe initial direction 1 1. The same result may be accomplished by movingthe rear plate away from or toward the front plate, as provided in Fig.5. In this case the rays which then fall on the neutral surfaces .9 swill be deflected upward toward the ceiling. It is possible also incertain cases to control the direction and intensity of the emergentlight by mounting the plates M N in frames Q Q, Fig. 15, intended to becircular and rotating one plate with reference to the other so that theprisms are no longer parallel. This method of control has the advantageof varying the light emerging from different portions of the rear platein different degrees. In other cases we may move one plate laterally aswell as transversely with reference to the other one, as by the pivotedlever arrangement shown in Fig. 12. In general there will be a variationin the quantity of light sent in any given direction whenever one platemoves with reference to the other along any line not parallel to thedirectionl in which the light emerges from the rear surface of the frontplate. This ability to control quantity of illumination in an apartmentis a valuable one where the intensity of the light changes during theday.

I do not here claim the use of coacting concave and convexdeflecting-faces, as this forms the subject of my application Serial No.694,880.

\Vithout limiting myself to the precise construction and arrangement ofparts shown, I claim as my invention 1. An illuminating structureconsisting of two opposing light-deflecting prismatic plates havinglight-receiving and emergent faces and an intermediate chamber, andmeans for shifting the plates to alter the cross-sectional outline ofsaid chamber, substantially as set forth.

2. An illuminating structure provided with parallel prismaticilluminating-plates,one adjustable in respect to the other to vary thequantity or direction of emergence of the light-rays and means forshifting the plates to any required extent, substantially as set forth.

3. The combination in an illuminating structure of a supporting-frameand two illuminating light-deflecting plates arranged in said frame toform a continuous closed intervening chamber the figured faces of bothplates within said chamber, substantially as described. 1

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

FRANK L. O. WADSVVORTH.

Witnesses:

E. G. FERGUSON, H. E. OARMAOK.

